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Re: RM and abstract syntax trees

From: Jonathan Leffler <jleffler_at_earthlink.net>
Date: Wed, 31 Oct 2007 21:31:32 -0700
Message-ID: <13iill2q6gusd6c@corp.supernews.com>


Marshall wrote:

> On Oct 31, 7:50 pm, David BL <davi..._at_iinet.net.au> wrote:

>> Isn't it helpful to see the analogy with a pointer dereference?
>>
>> I'll leave it up to you as to whether you dislike the analogy between
>> node identifiers and pointer values, and the idea that a join can be
>> compared to a pointer dereference.   Perhaps you are right and the
>> analogy creates confusion.

>
> I think if we are clear about it being an analogy we are on solid
> ground. But as soon as we start thinking pointers and references
> are the *same* thing we are in trouble, because now we can't
> see the differences anymore.
>
> I think Date actually nails this issue. He says (roughly) that
> pointers add complexity but don't add any expressive power.

Isn't the other 'point' that 'pointers point somewhere' but values stored in a relation don't - that relational database bases work on associative addressing. In particular, even in a foreign key, the value doesn't point to the referenced primary key; it merely contains the same value as some entry in the referenced table. It may also contain the same value as a large number of other places in the database.

-- 
Jonathan Leffler                   #include <disclaimer.h>
Email: jleffler_at_earthlink.net, jleffler_at_us.ibm.com
Guardian of DBD::Informix v2007.0914 -- http://dbi.perl.org/

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Received on Wed Oct 31 2007 - 23:31:32 CDT

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